Update: Instillation of Precision Aviation Inc. PAI 700 compass in the RV-12 instrument panel is a failure. However, an Airpath C2300 whiskey compass works just fine …. Go figure!
As mentioned in posts #3,11 & 17 of this thread, I wanted a backup compass in the RV-12 so a Precision Aviation Inc. PAI 700 vertical card compass was installed in the panel. The PAI 700 compass was installed in the upper left corner of the right instrument panel section above a backup altimeter and directly to the right of a backup airspeed indicator located in the upper right of the center panel section (photo can be seen in posts 3). Prior to installing the PAI 700, a check was made to verify the compass displayed the correct readings and had no tight spots … this was accomplished by slowly stepping around in a circle while holding onto the compass and all seemed well. Fortunately, I had the presence of mind not to cut out access holes in the panel for the adjusting screws because I was not sure if the compass could be swung … that proved to be smart.
I and others spent countless hours trying to make the PAI 700 compass work …. sadly to no avail. Initially, the RV-12 was taxied over to the compass rose where the SkyView’s magnetometer was ground calibrated and an attempt was made to swing the PAI 700 compass at that time ... north/south was basically spot on but east/west was WAY off by 15 degrees or so even after the east/west compensator on the compass was maxed out. Not good!
I’ll spare the forum all the troubleshooting methods used, but it did involve purchasing compensation balls which helped immensely but still did not solve the problem. Laying a sheet of Mu-metal across the top of the backup altimeter between the compass and the altimeter had the biggest affect and there was a point in time when I thought the compass would be usable using Mu-metal in conjunction with the compensating balls … but the compass began giving flaky non-repeatable readings, so decided it was time to throw the towel in.
Photo of the compensation balls attached onto the back of the PAI 700 vertical card compass:
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Photo of the Mu-metal that was installed under the PAI 700 vertical card compass.
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Decided to yank out the PAI 700 and replace it with an AirPath C2300 whiskey compass. Had much better luck with the C2300 which was able to be successfully swung … however, discovered it also required the sheet of Mu-metal installed across the top of the backup altimeter. Even with the Mu-metal in place the east/west compensator is maxed out … but most of the readings are within a couple of degrees now with the worst being 4 degrees off. So the Airpath C2300 compass is quite usable for a backup ... but nowhere near the “cool factor” of the PAI 700. In this case, it’s function over form.
Photo of the Airpath C2300 whiskey compass along with the Mu-metal which was necessary to allow the compass to be swung.
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New look of the DOG Aviation RV-12 front panel ... lost is the coolness of the vertical card compass .... gained is the functionality of the Pathway C2300 whiskey compass.
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